1. Field of the Invention
The present invention relates to an optical scanning apparatus mounted on an image forming apparatus such as a laser beam printer or a digital copier including an electrophotographic process means.
2. Description of the Related Art
In recent years, improvement in dust proof performance of the optical scanning apparatus is desired in accordance with increase in speed of the laser beam printer and diversification of the use environment.
As a conventional embodiment, an optical scanning apparatus described in Japanese Patent Application Laid-Open No. H11-242176 is illustrated in FIGS. 14 and 15.
As illustrated in FIG. 14, an optical scanning apparatus 140 emits laser light 130 from a fitted and assembled light source device (light source unit) 106. The laser light 130 emitted from the light source device 106 passes through a cylindrical lens 117 and provides a linear image on a reflection surface of a polygon mirror 115. The laser light 130 is deflected by rotating the polygon mirror 115, and is imaged and scanned on a surface to be scanned (e.g., photosensitive drum) (not shown) through a scanning lens 118 and a folding mirror 119, thereby forming an electrostatic latent image.
The light source device 106 emits the laser light 130 from a laser light source (not shown) serving as a light source, and the laser light 130 is converted to a parallel light flux by a collimator lens (not shown). As illustrated in FIG. 15, the laser light source is fixed to a laser holder 102 by using a known technology such as press-fit, and the collimator lens is fixed after being position adjusted with respect to the laser holder 102. The focus and optical axis adjustment of the laser light source and the collimator lens is thereby carried out.
When the polygon mirror 115 is rotated, the surrounding air is also stirred, and the air enters and exits an optical box (housing) 107. At the same time, dust at the periphery of the optical box 107 is also taken in, and such dust adheres to the polygon mirror 115, the scanning lens 118, and the folding mirror 119. The degree of adhesion is accelerated by the number of revolutions of the polygon mirror 115 and the extent of pollution of the air of the use environment. As a result, there may arise a problem that unevenness of light intensity is caused.
The main flow-in path of the dust from the vicinity of the laser light source is the gap between the light source device 106 and the optical box 107. In Japanese Patent Application Laid-Open No. H11-242176, an elastic member 114 is sandwiched between the fitted light source device 106 and the optical box 107 to prevent the dust from flowing into the interior of the optical box 107 from the flow-in path.
However, the following problems and restrictions still exist in the conventional technology described above.
In Japanese Patent Application Laid-Open No. H11-242176, the flow-in path that passes through the light source device itself barely exists, and the desired dust proof performance is achieved by simply sandwiching the elastic member between the light source device and the optical box.
However, such achievement is realized by adopting a system including a laser light source of a simple system, the system being configured such that the laser light source is press-fit to the laser holder, in Japanese Patent Application Laid-Open No. H11-242176. In other words, the press-fit region of the laser light source is in a substantially sealed state. Further, although the collimator lens is bonded at a minimum extent of only three points on the periphery and there is a gap region without adhesive on the periphery, a problem does not arise because this kind of the gap has an extremely small area.
Consideration of bonding the entire periphery of the collimator lens to enhance sealability is known. Such consideration can be made in the case where the collimator lens is sufficiently small, but is restricted if the collimator lens is a large lens such as a compound collimator lens in which collimator lenses of multiple systems are integrated.
When adopting the compound collimator lens, the laser light source side needs to be adjusted and bonded for adjusting the positions of the collimator lens of each system and the laser light source.
Therefore, in the configuration adopting the compound collimator lens, the flow-in path of dust that passes through the light source device itself exists, and improvement is desired from the standpoint of dust proof performance.